1. Technical Field of the Invention
The present invention relates generally to the field of communication networks and, more particularly, to a Media Access Control/Physical layer interface method and architecture.
2. Description of Related Art
FIG. 1 shows a diagrammatic representation of an open systems interconnection (OSI) layered model 10 developed by the International Organization for Standards (ISO) for describing the exchange of information between layers in communication networks. The OSI layered model 10 is particularly useful for separating the technological functions of each layer, and thereby facilitating the modification or update of a given layer without detrimentally impacting on the functions of neighboring layers. At a lower most layer, the OSI model 10 has a physical layer or PHY layer 12 that is responsible for encoding and decoding data into signals that are transmitted across a particular medium. Above the PHY layer 12, a data link layer 14 is defined for providing reliable transmission of data over a network while performing appropriate interfacing with the PHY layer 12 and a network layer 16. The Network layer 16 is responsible for routing data between nodes in a network, and for initiating, maintaining and terminating a communication link between users connected to the nodes. A Transport layer 18 is responsible for performing data transfers within a particular level of service quality. A Session layer 20 is generally concerned with controlling when users are able to transmit and receive data. A Presentation layer 22 is responsible for translating, converting, compressing and decompressing data being transmitted across a medium. Finally, an Application layer 24 provides users with suitable interfaces for accessing and connecting to a network.
The IEEE Local Area Network (LAN) standards divide the Open System Interconnection (OSI) data link layer into two sub-layers as illustrated in FIG. 1: the Media Access Control (MAC) 14b and the Logical Link Control (LLC) 14a. The LLC layer 14a is generally a software function that is responsible for attaching control information to the data being transmitted from network layer 16 to MAC layer 14b. The MAC layer 14b deals with the media access techniques utilized to control the access to a shared physical medium 26. The MAC layer 14b is primarily responsible for controlling the flow of data over a network, ensuring that transmission errors are detected, and ensuring that transmissions are appropriately synchronized. Token Ring and Ethernet are two legacy implementations of a MAC layer which use different methods to share the physical media. These two MAC types are typically implemented in an integrated circuit (IC) hardwired because of its technology maturity.
With technology development in the broadband communication area, bigger and faster data communication pipes are being established from homes and small offices to network servers and the Internet. The LAN technology has been extended to cover the home and small office environment, usually called Home Networking. The most prevalent high-speed home networking technologies in the industry are: HPNA 2.0/1.0, legacy Ethernet and 802.11 wireless LAN. These three technologies use a shared media access control method to access the physical layer phone wires, Ethernet cables and wireless media.
Although the MACs of these home LANs share some common features, each MAC maintains respective specialties. HPNA 1.0 and Ethernet MAC both use standard IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access with Collision Detection), which uses a binary exponential backoff algorithm to defer its transmission when media is busy. HPNA 2.0 MAC added a Distributed Fair Priority Queuing (DFPQ) deferring algorithm in addition to the CSMA/CD to provide the Quality of Service (QOS) guarantee at the physical layer. The HPNA 2.0 also generally allows two types of MAC architectures: a CSMA/CD with DFPQ type MAC and a standard 802.3 MAC with DFPQ Enhanced MAC (EMAC) or two layer MAC. Each has its advantages and disadvantages. IEEE 802.11 wireless LAN uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and NAV (Network Access Vector) technologies in the MAC layer for the assumption that each station cannot be guaranteed to be able to detect other stations in the wireless communications network.
In addition to the current requirements of the different MAC architectures and MAC implementations for various standards, development of the new home LAN technology, for example, is causing existing MAC standards to evolve and/or new MAC standards to emerge. Therefore, it would be advantageous to provide a new software based or programmable MAC implementation architecture which would speed up MAC implementation development, MAC/PHY and MAC/host integration, enable multiple MAC implementations, and increase MAC portability for different applications and platforms.